Practice exercise (made-up values, not clinical guidance). A 68 kg patient has a fluid goal of 35 mL/kg/day and receives all fluid through a feeding tube. The formula is 84% free water and runs at 85 mL/h for 20 hours a day. The rest of the fluid is given as water flushes every 6 hours. What volume V is each flush? Round to the nearest whole number.
68 kg35 mL/kg/day84%85 mL/h · 20 hevery 6 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 1200 mL of parenteral nutrition with final concentrations of 12.5% dextrose and 4% amino acids, plus 500 mL of 20% lipid emulsion (2 kcal/mL). Find the non-protein energy NPC in kcal per day. Round to the nearest whole number.
1200 mLdextrose 12.5%amino acids 4%lipid 500 mL · 2 kcal/mL
NPC = kcal/day
3.IV fluids & fluid balanceMedium
Practice exercise (made-up values, not clinical guidance). The record shows a patient's intake and output for one 12-hour shift. The IV infusion ran at the rate shown for the whole shift. Find the fluid balance B = intake − output in mL (a negative answer means a net loss).
Practice exercise (made-up values, not clinical guidance). A 500 mL infusion starts at 06:30 at 125 mL/h. After 2 hours the rate is changed to 50 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.
500 mL125 mL/h · 2 h50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 238 mL
Needs and free water: energy needs are often estimated as kcal/kg/day × weight and protein needs as g/kg/day × weight. A formula is only partly water, so its free water = volume × water fraction; water flushes make up the rest of the daily fluid goal. Ideal body weight (Devine): IBW = 50 kg + 2.3 kg for every inch over 5 feet (60 in) for men, and 45.5 kg + 2.3 kg per inch over 60 in for women; 1 in = 2.54 cm. The formula is meant for adults at least 152.4 cm (5 ft) tall. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Fluid goal
35·68 = 2380 mL/day
Free water from the formula
85·20 = 1700 mL
1700·0.84 = 1428 mL
Water still needed
2380 − 1428 = 952 mL/day
Volume per flush
24/6 = 4 flushes
V = 952/4 = 238 mL
Answer
V = 238 mL
2.Enteral & parenteral nutrition calculations
Answer: NPC = 1510 kcal/day
Parenteral nutrition: dextrose provides 3.4 kcal/g, amino acids 4 kcal/g and lipid emulsion the kcal/mL stated (2 kcal/mL for 20%, 1.1 kcal/mL for 10%). Grams = % × mL/100. Non-protein kcal (NPC) = dextrose + lipid kcal; nitrogen = protein/6.25. The glucose infusion rate (GIR) in mg/kg/min = dextrose mg/(kg × minutes). The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Grams of dextrose and amino acids
dextrose: 12.5·1200/100 = 150 g
amino acids: 4·1200/100 = 48 g
Kilocalories per component
dextrose: 150·3.4 = 510 kcal
amino acids: 48·4 = 192 kcal
lipid: 500·2 = 1000 kcal
Non-protein energy
NPC = 510 + 1000 = 1510 kcal/day
Answer
NPC = 1510 kcal/day
3.IV fluids & fluid balance
Answer: B = 685 mL
Intake and output: intake counts everything that goes in (oral fluids, IV infusions, IV medications and flushes, tube feeds); ice chips count as half their volume. Output counts urine, drains, vomit and other losses. Balance = total intake − total output; a negative balance is a net loss. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Total intake
oral: 150 + 150 = 300 mL
IV infusion: 80·12 = 960 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1360 mL
Total output
400 + 175 + 100 = 675 mL
Balance
B = 1360 − 675 = 685 mL
Answer
B = 685 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 7 h
Infusion time: time (h) = volume to infuse (mL)/rate (mL/h); use the volume still left in the bag, not the bag size. Volume infused = rate × time. Convert decimal hours to hours and minutes with the fraction × 60 (0.5 h = 30 min, not 50 min). The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
First part
125·2 = 250 mL
500 − 250 = 250 mL left
Second part
250/50 = 5 h
Total time
t = 2 + 5 = 7 h
Answer
t = 7 h
That is about 7 h 00 min, so the bag runs out at about 13:30.